Regeneration of spent adsorbent



April 25, 1961 v. L. BRANT ETAL 2,981,771

REGENERATION oF SPENT ADSORBENT Original Filed D60. 22, 1955 U ya@ Mww W i ATTORNEYS become apparent from` the tates 2,981,771 REGENERATIN F SPENT ADSREENT Victor L. Brant, Tulsa, kla., David G. Morgan, de-

ceased, late of Tulsa, Okla., by Madeleine G. Morgan and David L. Morgan, executors,` Tulsa, Okla.; said Victor L. Brant and David G. Morgan, assignors to D-X Sunxay (Bil Company, Tulsa, Okla., a corporation of Delaware Original application Dec. 22, '1955, Ser. No. 554,842.

Divided 835,812

9 Claims. (Cl. Zoll-683.52)

This invention relates to an improved method for the treatment of a hydrocarbon contaminated with sulfuric" acid, esters of sulfuric acid and related sulfur-bearing compounds, and, more particularly, it pertains toA the treatment of an alkylation product derived from the reaction of isoparaiiins and oleins in the presence of: sulfuric `acid to eliminate substantially the sulfur bearing contamisulfates. The total reaction product. is usually subjected to a separation treatment for the recovery of alkylate' product from the unreacted isoparain material. There-` fore, it is essential, in order to minimize corrosion ofthe equipment used for separation, that the` sulfur-bearing compounds and sulfuric acidbe eliminated substantially. In the past, the treatmentof alkylateifor theremoval of` contaminants hast been effected by caustic treatment.` It ywas found, however, that the caustic treatment isf not entirely satisfactory for the reasonkthat the non-acidic sulfur-bearing compounds,V `such as the dialkyl sulfatos;

are: not readily freactablewith the caustic material. under.V

the tconditionsnemployed.' As aresult, theselcompounds in the `allrylate decomposed under,` the conditions "of `sepa-1 rationand` formed corrosive products which caused operating diiculty in, for example, .thereboiler section of f the alkylation-fractionation tower. For this re`ason,.itis important that the contaminants in the alkylate product; notably the esters of sulfuric. acid, be removed substantially, otherwise, serious corrosionisexperienced' in the and this application July 24, 1959, Ser. No.:k

arent particularly dialkyl sulfate ester.

2,981,771 Patented Apr.. 25, 1961 CLC a product derived from the alkylation of an isoparafn with an olen by means of sulfuric acid contaminated with sulfuric acid, esters of sulfuric acid and related sulfurbearing compounds bythe method which comprises contacting the said oil with an adsorbent under such conditions that the hydrocarbon is in liquid phase and subf stantiallyall of the sulfur-bearing compounds` are ad` sorbed by the alumina. j

In another aspect of this invention, whenV the hydrocarbon oil containing sulfuric acid, esters of sulfuric acid and related sulfur-bearing compounds is contaminated with a substantial amount of sulfuric acid, it is initially treated for the removal of at least about70 percent of the sulfuric acid contaminant and thereafter the treated hydrocarbon is contacted with an adsorbent `under such conditions that the hydrocarbon is in liquid phase and substantially all of the sulfuric acid, esters of sulfuric acid and related sulfur-bearing compounds are adsorbed.

The present invention is particularly applicable for the treatment of a product derived from the alkylation of an isoparaiiin with an olefin by means` of sulfuric acid, which is contaminated with esters of sulfuric acid, `more This alkylation reaction is Iwellknown to those skilled in the art and it involves, for example, the reaction of an isoparain, eg., isobutane, isopentane, isohexane, etc., with an olefin, eg., propylene, butylene, amylene, etc., in thepresence` of sulfuric acid. The isoparaflin to olefin molar ratio is about 6 to about l000:1 and the sulfuric acid employed is about 50'to about 0.5 pounds of sulfuric acid per pound of olefin; The reaction is effected at a temperature of about 0 to about 100 F. and at a pressure of about O'to about 25 psig. The sulfur-ic acid is immiscible with the hydrocarbon material however, a portion thereof remains dispersed in the alkylation product along with y the mono and` dialkyl esters. Generally, the alkylation product contains between about 1.0 and about., 0 percent by weightfo-f sulfuric acid, more usually between` aboutOLl andabout 0.01 percent; 0.01 and about 0 percent Aby Weight of sulfur in other sufur-bearing compounds, more usually between about 0.005 and about 0.00lpercent.. The treatment with air adsorbent @serves not only to remove sulfur-bearing conrecovery equipment. It isithe purpose of this invention to t provide an irnprovedfmethod.by` which the difficulties.

mentioned hereinabove `aresubstantially overcome. f

It is an object of this invention to provide anwirnproved method for `th'e treatment of a' hydrocarbon* `oil `containmgl-sulfuric acid, esters .of` sulfuric,acidandrelatedsul fur-bearing compounds fortsubstantial removal ofthe.

contaminant. t k 4 u Another object of this invention 1s to d product derivedfrom sulfuric acid alkylation forlthe res` treat an alkylate moval of sulfuric acid, esters of sulfuric. acid and related` Ysulfur-bearingcompounds therefrom.` 1 i Other objects and advantages of i this` inventionwill planation thereof.` l. t vIt contemplated by, means of this `invention to -treat following `description and fex-` tarninantfin an `ecdnomi'cal Vand etlicientv manner, but also., itl improves quite unexpectedly the lead susceptibility or. esponse -of thealkylate much beyondgwhat is normally` expected., f i f l. 1 l.

The adsorbent materials'which are suitable forlcarryingiout this invention include absorbentaluminas, such,

as activatedtfalumina `and inorganic silicates, such as' aluminum silicate,` magnesium silicate or mixtures thereof.

These"materials do not provide equivalent results, however, and thej invention isvpreferably carried out byjtreating `coritanriiiated VhydrocarbonsV with alumina. Accordingly-themfollofwing `discussion is directed primarily to the use of this typeof material. This, however, isiiot to be construed as hunting the scope of the inv-ention.- p Y .In general,l the `alumina material to be used contains not `moreftlan about `10 percent by weight ofwater, and, more :partieularly,i` it `contains-about'6 to abouti 8. percent bygweight-ofwater, based on theftotal material. `Spe-` ciiically; the use ofwbauxitefas the adsorptive alumina is unusuallyeffective.` Bauxites, in general, contain about 40` tofabout 80 percent by weight of alumina andappre-'f` jciable` amounts oftwater ranging in amounts from about '1.5 to about 35 percent by weight.` Forthe purposegof thisinventon, the water concentration is lowered to the desiredrlevel by;` roasting` or calciningi` thewalumina or:

between about 3 Y bauxite at an Velevated temperature between about 500 and 1250 F. It is found that bauxite has exceptional properties for the adsorption of sulfuric acid, esters of sulfuric acid and related sulfunbearing compounds from the hydrocarbon alkylate and, in addition, it is successfully regenerated over appreciable periods of time without substantial loss ofV activity for the intended purpose. In general, the adsorption of the `sulfate material from the hydrocarbon alkylate is effected at a temperature of about 35 F. to about 350 F., preferably about 35 F. to about V130 F.; a pressure of about 0 to about 500 p.s..g.; and a residence time of about 0.5 to about 28 minutes, preferablyabout 3 to about 9minutes. In general, the quantity offoil being treated relative to the alumina or bauxite employed for the purpose is defined in terms of the weight space velocity, that is, the pounds of oil being supplied to a the treating zone per hour per pound of bauxite or alumina which is present therein.k The Weight space velocity is about 0.5 to about 30, preferably about 3 to about 10.

. While sulfuric acid is immiscible with hydrocarbon oils, nevertheless, in the alkylation reaction it tends to emulsify or become dispersed throughout the hydrocarbon oil and, for this reason, it is found that some sulfuric acid will pass to the treating zone containing the alumina material.

The passage of appreciable quantities of sulfuric acid toV the treating zone can have serious effects on the length of operation by shortening the effective life of the alumina. One method of prolonging the operating cycle is to employ bauxite or alumina containing a minimum concentration ofwat'er, that is, in the amount specied hereinabove. Inanoth'er aspect of this invention, the hydrocarbon oil to be' treated is preliminarily subjected to a separation treatment for the removal of at least about 70 percent of the sulfuric acid contained in the hydrocarbon feed. More usually, the separation treatment results in the removal of 75 to about 95 percent of the sulfuric acid.

"An effective' method for the removal of'sulfuric acid is by means of a coalescer. The coalescing means may be varied in nature, however, in general, it may comprise a mat or a body of glass wool or steel turnings, or any material which will furnish or supply surface area to the hydrocarbon oil passing therethrough. The coalescing means are Well known to those skilled in the art and, for this reason, it is not believed necessary to define their construction in detail. VIn general, the separation of sull furie acid from -the hydrocarbonoil by means of coalescers iseiected ata temperature of about F, to about 250 F.; a pressure'of about Oto about 500 p.s.i.g. and at linearflow rate of aboiit 0.01 to about feet per second or below the velocity at which mixing occurs due to impingement.V rAs kpreviously indicated, the removal of sulf uric acid reduces'p'roportionately lthe tendency for the sulfuric acid to shorten the effective life of the alumina.

l AAfter the alumina or bauxite has been used for an appreciable periodo-f time and large quantities of sulfur` bearing contaminants are adsorbed thereoii,it becomes necessary to regenerate the alumina. In this respect, it should be noted that bauxite is unusually effective for the treatment of hydrocarbon oils in accordance with this invention for the reasonthat it can be regenerated repeatedly and still retain to a substantial extent Vits original adsorptive activity. l Since the treatment of the hydrocarbon oilv is effected under liquid phase conditions, the

. firstA step in the regenerationV procedure is to empty the treating zone` of'all-liquid material. After the treatingY Azonehasfbeen, emptied of hydrocarbon oil, the alumina or bauxiteis vwashed with water at a temperature of `about 40? to'about 210 F. and for a period of about 15 minutes to` about 20'=hours. VWater is a polar material which is preferentially adsorbed on the alumina or bauxite, consequently, it;ser.ves to displace the. sulfur-bearing contam` inants-which are'adsorbed `on the alumina. The desorption of. contaminants by meansofwater Vis accelerated as the temperature is increased; andY forthat reason, itis preferred .that the water treatment be effected in a series of steps of increasing temperature. In this respect, the first phase or step is effected at a temperature between about 40 F. and 100 F. and for a period of about 15 minutes to about 10 hours. A low temperature is used in the rst step in order to avoid undue temperature rises which may occur from wetting the alumina with water. The second step is effected at a temperature of about 100 F. to 210 F. and for a period of about 15 minutes to 10 hours. While two steps of washing with water have been given it should be understood that within.

each step, the temperature may be raised gradually or abruptly and the temperature at various stages of treatment may be varied in any manner desired, or the wash ing can be effected as a single step with the temperature being gradually raised. Alf-ter the alumina or bauxite has been treated with water, and it is apparent from, the effluent that a substantial part or all of the sulfur-bearing contaminants have been removed, the alumina is optionally treated with steam -for the purpose of removing appreciable quantities of water therefrom and/or to lassist in removing contaminants from the alumina. The steam treating step is effected at a temperature of about 220 F. to about 500 F. and for a period Iof about 0.5 to about 15 hours, more usually about 1 to about 10 hours. The steam treatment is conducted for a period sufficient to remove a substantial amount of water which is wet ting the alumina andto desorb more sulfur-bearing cornpounds, if present. alumina'or bauxite is treated with .a gas at an elevated temperature of about 200 F. to about 1000 F., more usually about 300 F. to about 500 F. and for a period of about 1 to about 30 hours vfor the purpose of drying or desorbing substantial quantities of water. The gas used may be any inert gas capable of replacing the water present on the alumina, such as, for example, flue gas,

nitrogen, natural gas and, in general, gaseous hydrocarbons containing not more than 2 carbon atoms. After the alumina or bauxite has been dried by means of the gas, it isthen optionally cooled by passing the gas at a lower temperature therethrough for a period of about 0.5

i contaminated hydrocarbon koils in general. lInthis reto about 10 hours. The temperature of the gas falls within the same range which is used for the treatment of hydrocarbon oil with the, alumina, that is, in general, a temperature of about 35 F. to about 120 F. After the alumina or bauxite has been cooled by means Vof the gas, it is ready for the treatment of a contaminated hydrocarbon alkylate. Y.

Whilethe preceding discussion has been limited to a consideration of treatment of a hydrocarbon alkylate restricted Yin scope thereby.V This portion of the invention is intended to include the regeneration of alumina which' has become spent through the .treatment `of sulfur spect,:the hydrocarbon .can Vbe one which has been pre-V viouslytreated with sulfuric acid, suchas, for example,` gasoline, naphtha, kerosene, gas oil, lubricatingroil, etc.

The method of treatment of the lhydrocarbon fraction by:

g means of sulfuric acid is well known to those skilled in the art, and, therefore, it is not necessary to` describe herein the conditions of treatment.v

In orderto provide a better understanding Yof thisjin-1 vention, reference will be had to the accompanying drawing which contains anillustration of the present invention. v .Y

In the drawing;sulfuric acid, having a titrable acidity of percent, Yis fed from source 5-at the Yrate `of 30,000

pounds per hour, and this material lis 'charged to an. alkylation reactor shown schematically as zone Y7.Y 'Ag butylene feed material isfed tothe alkylation zone 7 by means `of line 9 at the rate of 5000 barrels per Lday..y Similarly, the isobutane feed is fedvfromvsource /10 at' tli'e"iate fof-12,000 barrels Vper day. 'In ...the alkylation Following the steam treatment, thev and which is useful as aviation fuel or for blending to produce motorfuel. The alkylate is discharged from they alkylation zone by means of line 12; whereas the sulfuricV acid which is separated therefrom is discharged from the alkylation zone by means of line 14. The

alkylate product contains about 0.02 percent by weight' of emulsied sulfuric acid and about 0.002 percent byweightof sulfur in other sulfur-bearing compounds, principally esters of sulfuric acid. The alkylate material is charged to a coalescer shown schematically as 15 and which contains glass wool having an approximate fiber diameter of about 0.00025 inch.` Thecoalescer is maintained at a temperature of about 40 F. and at a pressure of about 175 p.s.i.g. The alkylate passes through the coalescer at asuperlicial linear velocity of about 0.12` feet per second.` v

As a resultof'the operatingconditions in the coalescer, approximately 80 percent of the sulfuric acid originally contained therein is removed. The treated alkylateis discharged from the coalescer by means of line 16 and it flows to a header 18.` The header 18 is connected to lines 20and 21 which' are, in turn, connected to the top of treaters23 and 24, respectively. Eachof these treaterscontains 8000 pounds of bauxite, occupying a volume of about 140 cubic feet. The bauxite has a mesh size of about 20/ 60 and it contains `-in its original dehydrated condition about '6 percent water. The entry lines 20 and 21 which are connected'to the top,4 of treaters 23 and 24 contain valves26 and 27, respectively.` Treaters23 and 24 are operated alternately such that while one of them is being regenerated, the other is being used for` the adsorption of sulfur-bearing contaminants from the alkylate. In this example, treater 23 is being used for the removal of contaminants from the `alkylate product. Accordingly, valve 26 is in an open position, whereas valve 27 is` closed. Further, the treated alkylate `is passed from the bottom ofthe treaters 23 and 24 by means of lines 30 and 31, respectively. These lines also contain valves 33 and 34. In operation, valve 34 is closed, whereas valve 33is open, consequently, the treated alkylate passesinto` header B6 before being discharged from the system by means of line 37. The `quantity of valkylate being charged .to treater 23 provides a weight space velocity of about 6. Further, the alkylate entering treater 23 contains about 0.004 percent by weight of sulfuric acid and about 0.002 percent sulfur in other sulfur bearing contaminants. The temperature in treater 23 is about 40 F. and the pressure is about 175 p.s.i.g. Under these conditions, the alkylate product is in a liquid phase, and the alkylate leaving treater 23 contains 0.0001 percent sulfur in sulfur bearing contaminants,

thus showing Vthe unusual effectiveness of bauxite for this purpose.

For the purpose of regeneration, steam, water and methane are supplied from lines 40, 41 and 42 and these, in turn, are connected to a header 43. One `of the regeneration materials flows from supply header 43 to line 45, which in turn divides into lines 46 and 47. Lines 46 and 47 contain valves 48 and 49, respectively. Since treater 24 is being regenerated, valve 4S is closed, whereas valve `49 is in an open position. The regeneration uid is discharged from the bottom of treaters 23 and 24 by means of lines30 and 31, respectively. The regeneration fluid is passed from line 30 to line 50 and regeneration of bauxite-in treater 24 effected in accordance with the following schedule:

Steps Rate Tsl'p., Time, Hrs;

1 Emptylng Contaetor. -g.p.h 420 45Y 2; 5 2. Water Wash g ..g.p.h 1, 500 v80- 1.5 3. Water Washing..." g.p.h.. 1, 500 0. 6 4. Water Washtn g.p.h.. 1, 500 125 0. 5 5. Water Washing g.p.h.- 1, 500 0. 6 Water Washing g.p.h 3, 000 17'5` 0. 5 7. Water Washing g.p.h.` 3,000 200 0'. 5` 8. Water Washing-- g.p.h.. 5, 000 200 1.0 9. Steam Heating .#lhxz max; 5,000 350 6.0 10. NaturalGas Drying -.s.e.f.h; 25, 0001 350 l 12.0 to 14.0r 1l. Natural Gas Cooling s.c.f.h.. 25,000 80 5.0

l Dry 2.0 hours after bauxite reachestemperature of about 290 F.

. Having thus. provided adescription of this. invention, it should be understood that no undue limitations or restrictions are to be imposedby reason thereofbut that the scope of the invention is defined by the appendedl claims. t

We claim:

1. In a process` for the allcylation of an isdparatlinwith` an olefin in the presence of sulfuric acid in'whicl:ttthel resulting alkylate product is passedthrough alumina for the removal of sulfur-containing contaminants, theim provements comprising regenerating alumina spent by` adsorbing said contaminants by contacting the samelwith' water at a temperature of about 40 F. to abou't210? F. for a` period of about15 minutes to about 20 hours, treat-V ing the washed alumina with a steam at ai temperature:`

of` about 220 to about 500 F. for about .5 to 15,v

hours, `and treating the steam-treated alumina withan inert ,gas at a temperature of about 200` F. to about treating the washed alumina with steam ata tempera'` ture of about 220 F. to about' 500` F. for about 1 to l0 hours and treating the steam-treated alumina with an inert gas at a temperature of about 300 F. to about 500 F. for a period of about l to 30 hours.

3. In a process Ifor the alkylation of C4 to C8 isoparans with C3 to C5 olefns in the presence of sulfuric acid catalyst in an alkylation zone in which the alkylate i product is contaminated with sulfur-bearing compounds* and in which said product is fractionated in a fractionating zone, the improvement which comprises separating the major portion of said sulfur-bearing compounds from said alkylate product by passing said alkylate product through a liquid phase coalescing zone at a temperature in the range of from about 0 P, to about 250 F., separating an alkylate product containing a minor amount of said sulfur `contaminants from said coalescing zone and con- -tacting the same with an adsorbent material under liquid phase conditions to remove substantially all of the sulf fur-bearing compounds from said alkylate product by adsorption, recovering alkylate product substantially free of sulfur contaminants from said adsorption step, fractionat-ing the last mentione'dproduct in said Vfractionating zone at an elevated temperature, Washing the adsorbent thence, it can be discharged from the system by means of line 51. Line 50 contains valve 52. On the other hand, regeneration Huid can pass from treater 24 to iline A,70 31 and, in turn, line 31 is connected to line 54 containing valve 55. In the present example, valve 52 in line 50 is a in Va closed position, whereas valve 55 in line 54 is open,

l and, therefore, the regeneration uid from treater 24 is discharged from the system by means of line 51. The

steamtreating step by contacting the same with a gaseous hydrocarbon containing not morethan'about 2 carbon ,atoms per molecule ata temperature between. about 200 and about 1000 F;, -cooling said .adsorbent material and employing the cooled adsorbent material to adsorb additional sulfurbearing compounds from. alkylate product.

4. In a process for the alkylation of C4 to C6 isoparafs'with C3 to C5 olefins in the presence of a sulfuric acid catalyst in which an alkylate product contaminated with sulfur-bearing compounds is recovered from the alkylation zone and is contactedv with an 'alumina adsorbent,

the improved method vof regenerating the alumina for reuse which comprises contacting said alumina with water to. desorb substantially all of said sulfur-bearing compounds, contacting said water-treated alumina with steamv at an elevated temperature of from about220 F. to about 500 F., and drying siad steam-treated alumina by direct contact with a gaseous material selected from the group consisting of ue gas, nitrogen, natural gas, and gaseous hydrocarbons containing not more than 2'carbon atoms per molecule.'4

"5. Thcfmethod of claim 4 in which the alumina is bauxite, j j t.

`6. In a process for the alkylation of C4 to C6` isoparaflins with C3 to C5 olens in the presence of a sulfuric acid'catalyst in which an alkylate product contaminated with sulfur-bearing compounds is recovered from the alkylation zone and is contacted with an adsorbent, the improved method of regenerating the adsorbent for reuse which comprises Washing said adsorbent with water at a temperature between about 40 F. and about 210 F., contacting said water-washed adsorbent with steam at an elevated temperature of from about 220 F. to about 500-F., and thereafter drying the steamtreated adsorbent by direct .contact with lan inert gaseous material atl a temperatureV between about 200 F. and about 1000 F. to reduce the water content of the adsorbent below about' 10 percent by weight. g

7.' Ina process for the alkylation of C4 to C6 isoparains with C3 to C5 oleiins in the presence of a sulfuric acid catalyst in which an alkylate product contaminated with 'sulfurbearing compounds is recovered from the alkylation zone and is contacted with a bauxite-adsorbent; the improved method of regenerating the bauxite for reuse which comprises contacting said contaminated bauxite rstwith water at a temperature in the range of from about 40 F. to about 100, F., thereafter raising the temperature `of the water wash tofrom-about l100,* F. to about 210 F., contacting the water washed bauxite with steam at a temperature of from about ,200"A F. to -about'500 F., drying said steam-treated bauxite'lby direct contact with a gaseous material at a temperature in the range of from about'300 Esto about 500 yF., and theref aftercooling saidl dried'bauxite under conditions such that said bauxite contains less than 10 percent by weight ofwater. 1 ,i V8. In a process for the alkylation of an isoparain with an olefin in the presence of a sulfuric acid catalyst in which an alky-late product contaminatedwith sulfur-bearing compounds is recovered from the alkylationzoneand is contacted with an adsorbent, the improved method of regenerating the adsorbent for reuse which comprises contacting said adsorbent with water to desorbsubstantially all of said sulfur-bearing compounds, contacting saidv water-treated adsorbent Awith steam atan elevated temperature of from about 220 F. to about 5005 F., and drying said steam-treated adsorbent by direct contact with an inert gaseous material at a temperature between about 200 F. and 1000 F. Y

f 9'. In a process for the alkylation of an isoparain with an olefin in the presence vof a sulfuric acid catalyst in which an alkylate product contaminated with sulfur-bearing compounds is recovered from the alkylation zone and is contacted with an adsorbent, the improved method of regenerating the adsorbentfor reuse which comprises contacting said adsorbent with water to desorb substantially all of said sulfur-bearing compounds, contacting said water-treated adsorbent with steam atan elevated temperature of from about 220 F. `to about 5009 F., and thereafter cooling said dried adsorbent under conditions such that said adsorbent contains less than 10% by weight of water.

References Cited in the iile of this ypatient. n Y

UNITED `STATES PATENTS 1,868,581 Miller July 26, 1932 2,381,256 Callaway Aug. 7, 1945 2,393,154 Franklin Ian. 15, 19,46 2,398,495 DOuville et a1. Apr. .16, 1946 2,700,690 vMottern Jan, 25, 1955 

1. IN A PROCESS FOR THE ALKYLATION OF AN ISOPARAFFIN WITH AN OLEFIN IN THE PRESENCE OF SULFURIC ACID IN WHICH THE RESULTING ALKYLATE PRODUCT IS PASSED THROUGH ALUMINA FOR THE REMOVAL OF SULFUR-CONTAINING CONTAMINANTS, THE IMPROVEMENTS COMPRISING REGENERATING ALUMINA SPENT BY ADSORBING SAID CONTAMINANTS BY CONTACTING THE SAME WITH WATER AT A TEMPERATURE OF ABOUT 40*F. TO ABOUT 210*F. FOR A PERIOD OF ABOUT 15 MINUTES TO ABOUT 20 HOURS, TREATING THE WASHED ALUMINA WITH A STEAM AT A TEMPERATURE OF ABOUT 220*F. TO ABOUT 500*F. FOR ABOUT .5 TO 15 HOURS, AND TREATING THE STEAM-TREATED ALUMINA WITH AN INERT GAS AT A TEMPERATURE OF ABOUT 200*F. TO ABOUT 1000*F. FOR A PERIOD OF ABOUT 1 TO 30 HOURS. 